Pneumatic biasing system for a screw blank cold heading machine

ABSTRACT

A machine for cold heading screw blanks includes a sliding punch which is driven against a fixed die. The punch and die are apertured to receive and enclose the screw blank as a punch pin operates within the punch aperture to upset the screw blank and form a partially finished head thereon in a recess located on the forward face of the punch. An improved biasing means incorporated into the machine comprises a pneumatic system which introduces pressurized air into a confined space behind the sliding punch. The pressurized air biases the punch forwardly against the fixed die to assure that the screw blank is completely confined as the screw head is formed. An improved lubrication system supplies oil behind the sliding punch along with the pressurized air.

Elite States atent Rose 1 Sept. 23, 1975 Primary Examiner-C. W. Lanham Assistant ExaminerE. MI Combs [76] Inventor: Joel S. Rose, 9806 Cedar Dr.,

Overland Park, Kam- 66207 Attorney, Agent, or Firm-Lowe, Kok er, KIrcher et a1.

[22] Filed: July 5, 1974 [57] ABSTRACT [21] Appl. No.: 485,800 A machine for cold heading screw blanks includes a sliding punch which is driven against a fixed die. The punch and die are apertured to receive and enclose [52] US. Cl; 10/2; lO/ll R; 10/26 the Screw blank as a punch pin Operates within the [51] Int. Cl. 823G 9/00; 1321K 1/44 punch aperture to upset the Screw blank and form a [58] Flew of Search 11 11 12 partially finished head thereon in a recess located on IO/IZ-SI 26 the forward face of the punch. An improved biasing means incorporated into the machine comprises a [56] References Cted pneumatic system which introduces pressurized air UNITED STATES PATENTS into a confined space behind the sliding punch. The 1,026,872 5/1912 Leyner 10/15 pressurized a ias s th punch forwardly against the 2,165,424 7/1939 Tomalis v 10/24 fixed die to assure that the screw blank is completely 2,3 5,7 2/1946 BuCh t l0/l1 R confined as the screw head is formed. An improved 2,886,836 5/1959 Moeltzner lO/Z lubrication systgm supplies il the FOREIGN PATENTS OR APPLICATIONS Punch along with the pressurized 476,265 5/1929 Germany 10/11 R 4 Claims, 9 Drawing Figures 22 la i,-

24 29 as 1 +43 14- 1 l 26 3O /v l5 1 Rk 2a 1a a k 27 Q 2/ l7 4 as Sheet 1 of 2 Sept. 23,1975

US Patent US Pawn Sept. 23,1975 Sheet 2 of2 i fififififi 35 COMPRESSOR f REGULATOR gfggy i PUNCH BLOCK 37 38/ 39 PNEUMATIC BIASING SYSTEM FOR A SCREW BLANK COLD I-IEADING MACHINE BACKGROUND AND SUMMARY OF THE INVENTION This invention relates generally to an improvement in a machine for cold heading screw blanks and more particularly to an improvement in the biasing means acting on the sliding punch which are generally incorporated in machines of the type shown in US. Pat. No. 2,165,424.

Machines such as that disclosed in the abovementioned patent, which issued July 11, 1939, to Tomalis, have long been used to form heads on screws by means of a cold heading process. As described in the patent, a screw blank formed of wire stock is cut to the desired length and held in axial alignment between a stationary die and a moving punch, both of which include apertures sized to receive the screw blank. The moving punch is slidably disposed in a punch block which is driven toward the die to cause the screw blank to enter the apertures of the punch and die. After the forward end of the punch has been moved into flat engagement with the die, the screw blank is engaged by a punch pin that slides within the punch aperture. Further forward movement of the punch pin forces the end of the confined screw to become deformed and flow into a recess in the end of the punch which is appropriately shaped to form a semi-finished head on the screw. A second punch is then rammed into the screw head to finish the head and provide a slot or recess therein for receiving a screwdriver.

The present invention relates to the sliding punch which is biased forwardly during the cold heading operation, holding same against the die to completely en close the screw blank as the head is formed thereon. Without the biased arrangement described above, the head would expand beyond the recess in the end of the punch, as it was being formed, to an irregular shape andenlarged size. The presently existing practice is to interpose a compression spring behind the punch to achieve the required biasing force.

The provision of a spring to bias the sliding punch has proven unsatisfactory for a number of reasons including the frequent problem which occurs when the spring breaks or otherwise fails. Since the machine typically operates at a rapid pace to cold head screws in lots of at least several hundred thousand, the spring is subjected to repeated tension and compression. As a result of this repeated stress, the spring frequently breaks without warning and the screws formed immediately thereafter are ruined due to improper head formation. Aside from the significant quantity of screw stock wasted, the machine must be completely shut down in order to replace the broken spring. This cumbersome spring replacement problem not only wastes valuable machine time but also causes considerable inconvenience to the operator who must disassemble certain components, remove the broken spring, install a new spring, and reassemble the components before the machine can resume operation. As a result, valuable production time is lost as-well as expensive parts need to be replaced.

Even before the spring is worn to the point of breaking, the repeated reciprocating force exerted thereon causes the spring to become fatigued and lose its strength. Since the fatigued spring cannot function properly to retain the sliding punch in the required position, the screw heads are deformed and likewise must be discarded, resulting in further material waste. The cost of the overall process is also increased because the finished screws must be closely and regularly inspected to determine whether the spring has weakened or failed.

. An additional problem associated with using a spring is that the spring force varies depending on the degree of compression. The punch upon which the spring operates will therefore tend to vibrate somewhat and move slightly from its proper position as the spring force varies with the rapid operation of the machine. Also, since each different diameter of screw that is to be cold headed requires a different biasing force on the punch, the spring must be replaced every time a different length of screw is to be operated upon. Of course, this further adds to the shut-down time of the machine and the inconvenience to the operator who must substitute springs with each different job order.

' Cooling and lubricating the working components is a still further advantage of the subject invention. Due to their rapidly sliding movement, and friction from the upsetting of steel, the punch and spring become heated to excessive temperatures during operation of the machine. Additionally, existing lubrication systems do not apply sufficient quantities of lubricant to the punch recess, the punch pin, or the punch aperture (in which the punch pin slides) because of their inaccessibility. Foreign material such as dirt, caked oil, and the like tend to build up behind the punch and in the aperture thereof, and additional shut-down time is required to regularly clean the components. Since dirt causes wear on the components, the pressurized air-oil mixture sub stantially eliminates this problem. Also, the subject lubricating technique significantly increases the life of the moving parts.

When extremely short screws are to be cold headed, there is insufficient clearance between the sliding punch and the carrying structure that holds the screw blank. It is therefore necessary to bias the punch pin forwardly to protrude beyond the forward end of the punch so that the pin will engage the screw blank and push it into the aperture of the stationary die prior to the punch being moved forwardly enough to engage the screw blank. The blank is then supported in the die, and the carrying structure can be withdrawn before the punch collides therewith. The necessary biasing force on the punch pin is presently provided by a second spring which is interposed behind the pin near the first spring. Besides compounding the problems previously.

mentioned, this arrangement results in substantial interference between the two springs and has proven so unsatisfactory that the use of a non-sliding punch for short screws frequently presents fewer difficulties, even though the resulting screw head is deformed and must be cropped or trimmed.

In view of the aforesaid difficulties long associated with cold heading machines, it is a primary object of the present invention to provide, in a machine for cold heading screw blanks, an improved biasing means for achieving the required forward force on the sliding punch incorporated in the machine.

Another object of the invention is to provide, in a machine for cold heading screw blanks, a biasing means for the sliding punch which eliminates the spring failure problems heretofore associated with such machines.

Still another object of the invention is to provide a biasing means of the character described that operates to exert a constant force on the sliding punch.

Yet another object of the invention is to provide a biasing means of the character described wherein the force exerted on the sliding punch may be quickly and easily adjusted. This important feature. accomplished simply by adjusting the air pressure, greatly facilitates switch-overs between different screw diameters.

A further object of the invention is to provide, in a machine for cold heading screw blanks, an improved means for cleaning, cooling an lubricating the sliding punch and associated components. It is a significant feature of the invention that the lubricant is introduced behind the sliding punch and is dispersed by the pressurized air and forced through the punch aperture and recess to cool and lubricate the aperture and recess in conjunction with the air.

A still further object of the invention is to provide, in a machine for cold heading screw blanks, an improved means for biasing the punch pin forwardly to protrude beyond the forward end of the sliding punch when short screws are operated on by the machine.

Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.

DETAILED DESCRIPTION OF THE INVENTION In the accompanying drawings, which form a part of the specification and are to be read in conjunction therewith and in which like reference numerals are employed to indicate like parts in the various views:

FIG. I is a sectional view through the sliding punch assembly and fixed die of a cold heading machine, with a screw blank of normal length positioned between the punch and die;

FIG. 2 is a fragmentary sectional view similar to FIG. 1, but with the punch moved against the die and the screw blank confined within the punch and die as the upsetting operation begins;

FIG. 3 is a fragmentary sectional view similar to FIG. 2, but with the upsetting operation completed;

FIG. 4 is an elevational view taken generally along the line 4-4 of FIG. 1 in the direction of the arrows;

FIG. 5 is a fragmentary sectional view through the sliding punch assembly and fixed die of the cold heading machine, with a short screw blank positioned between the punch and die and a modified punch pin included in the punch assembly projecting beyond the forward end of the punch;

FIG. 6 is a top plan view, partially in section, taken generally along line 6-6 of FIG. 5 in the direction of the arrows;

FIG. 7 is a fragmentary sectional view similar to FIG. 5, but with the punch moved against the fixed die and the screw blank confined within the punch and die as the upsetting operation begins;

FIG. 8 is a fragmentary sectional view similar to FIG. 7, but with the upsetting operation completed; and

FIG. 9 is a schematic diagram illustrating the various components of the pneumatic and lubricating system included in the present invention.

Referring now to the drawings in detail and initially to FIGS. l4, a machine used to form heads on screw blanks by a cold heading process is partially illustrated and generally designated by reference numeral 10. The basic structural configuration of machine 10 is similar to that of the machine disclosed in U.S. Pat. No. 2,165,424, which issued July 11, 1939, to Tomalis, and to which reference may be made to gain a more detailed understanding of the overall structure beyond that illustrated in the drawings.

Machine 10 includes a stationary die holding structure II which is secured adjacent a backing structure 12 and in spaced relation with respect to a reciprocating gate 13. Die holding structure 11 is provided with a cylindrical opening in which a fixed die 14 is received and retained. Die I4 has a central aperture 15 in which a knockout pin 16 is closely received, while a backing member 17 positioned behind die 14 is also apertured to receive knockout pin 16. Backing structure 12 is provided with a bore 18 for receiving the enlarged base portion 160 of knockout pin 16. Knockout pin 16 is ad justable as to its position in die aperture 15 in order to accommodate different lengths of screws. The knockout pin may be fixed in position at any desired depth within aperture 15 to permit a screw blank to enter aperture 15 a distance equal to the desired screw length. An ejector mechanism (not shown) of conventional operation acts on knockout pin 16 to eject a completed screw from die 14.

In more conventional cold heading machines, and as can be seen by referring to the aforesaid Tomalis patent, a second fixed die (not shown) having an aperture therethrough is mounted in die holding structure 11 at a position offset to the side of die 14. A supply of wire stock is intermittently fit through the aperture in the second die by any well known mechanism and cut to the desired length by a knife (not shown) to form a screw blank 19. A carrying structure 20 (FIG. 6) of a conventional type is associated with the knife and operates to carry screw blank 19 sidewardly and hold the same in axial alignment with die aperture 15, which is of a diameter to closely receive blank 19 as the blank is further operated upon.

The reciprocating gate 13 is secured to a punch block 21, as by a pair of bolts 22. Gate 13 is driven by a drive mechanism such as a crankshaft (not shown) which is well known in the art and which is operable to drive the gate (and the punch block 21 carried thereby) in reciprocating motion toward and away from the stationary structure 11, as well as rotatably with respect thereto. The forward portion of punch block 21 is provided with a cylindrical opening 23in which a sleeve 24 is secured. A circular backing plug 25 is retained in a fixed position behind sleeve 24 at the rearward end of opening 23.

A generally cylindrical punch 26 is closely fitted within sleeve 24 but is slidable therein for limited axial movement within opening 23. Punch block 21 and sleeve 24 are provided with a transverse opening in which a pin 27 is removably inserted. The sliding punch 26 has a flat groove 28 formed in the bottom thereof for engagement with pin 27 to limit the outward movement of punch 26 with respect to opening 23. Pin 27 and groove 28 also engagingly cooperate to prevent rotation of the punch in the punch block opening. Punch 26 has a cylindrical cavity 29 formed in its rearward end and extending longitudinally throughout substantially the rearward half of the punch. Cavity 29 terminates forwardly in communication with a small aperture 30 which is formed centrally within punch 26 and extends longitudinally therein substantially throughout the forward half of the punch. Aperture has a diameter sized to closely receive screw blank 19 as the blank is operated on. The forward end of aperture 30 terminates at a recess 31 formed centrally in the forward face of punch 26. Recess 31 may be of any selected configuration depending on the desired shape and size of the partially finished screw head. The forward end of punch 26 may be rounded or beveled at the edges, although a flat surface on the forward end of the punch surrounds recess 31 and is considerably larger than the recess.

A punch pin 32 is received in aperture 30 and cavity 29 of punch 26. The forward end of punch pin 32 is sized to closely but slidably fit in aperture 30, while an enlarged cylindrical collar 32a formed intermediately on the punch pin is smaller in diameter than cavity 29. The punch pin has a flanged circular base 321) which is formed at the rearward end of collar 32a and which presents a flat rearward surface. Base 32b is of enlarged diameter relative to the remainder of the punch pin and closely fits in cavity 29.Outward movement of punch pin 32 relative to punch 26 is limited by engagement of the collar 32a with the shoulder formed between cavity 29 and aperture 30, a position wherein the forward end of punch pin 32 extends to the rearward edge of recess 31. The overall length of punch pin 32 is equal to the distance between the rearward edge of recess 31 and the back end of punch 26.

The present invention is concerned principally with the provision of a pneumatic system for biasing punch 26 (and in some cases punch pin 32) forwardly in punch block opening 23. Punch block 21 and sleeve 24 have a small passage 33 formed therethrough. Passage 33 connects at its inward end with the extreme rearward end of opening 23, adjaeently forwardly of the front surface of backing plug 25. Passage 33 extends generally downwardly from opening 23 and entirely through sleeve 24 and punch block 21 to terminate at the bottom surface of the punch block. An airtight fitting 34 is threaded into the bottom of punch block 21 in communication with passage 33. Fitting 34 is in turn sealingly secured to a hose 35 which is flexible. Hose 35 forms a portion of the pneumatic line and extends to connection with a lubricant source and an air source, which are illustrated schematically in FIG. 9.

The components shown schematically in FIG. 9 are conventional devices of well known types. A conven tional air compressor 36 may be of any suitable type which operates to supply pressurized air to the pneumatic line. Compressor 36 includes an on/off valve 37 for controlling its operation. An adjustable pressure regulator 38 is disposed in the pneumatic line and is operable to maintain a constant air pressure therein. Pressure regulator 38 is preferably associated with a gauge (not shown) which indicates the pressure of the air passing through the pneumatic line from the compressor. Since it is desirable to lubricate opening 23 of punch block 21, a lubricant source 39 is preferably included in the system to provide a lubricant such as oil. Lubricant source 39 may be of a conventional type that is adjustable to feed varying quantities of oil into hose 35, depending on the amount of oil required to properly lubricate the components. The pneumatic system is thus operable to supply air at various pressures to punch block opening 23 and behind punch 26 and punch pin 32 to bias the punch and punch pin for wardly as the machine operates. Oil is also supplied to opening 23 in the desired amount, being forced through hose 35 by the pressure of the air therein.

As is common in cold heading machines, a second punch 40 (FIG. 4) is included to finish the screw head and form a recess or slot therein for receiving a screwdriver. Punch 40 is preferably mounted in an opening in a second punch block 41. Punch block 41 is secured to the reciprocating gate 13 at a position slightly above and to the side of punch block 21, as by a pair of bolts 42. The forward end of punch 40 is provided with a central recess 43 sized and shaped similarly to recess 31 of punch 26. Recess 43 further includes a projection 44 in the shape ofa screwdriver receiving slot or recess which is to be formed in the screw head. The drive mechanism which carries the reciprocating gate 13 operates to effect a sequential cycle wherein punch 26 is moved against die 14, punch .26 and punch block 23 are withdrawn rearwardly, punch block 41 is rotated over such that the recess 43 of punch 40 is aligned with aperture 15 of die 14, punch 40 is moved against the die 14, and punch block 41 and punch 40 are withdrawn rearwardly.

When short screw blanks such as the blanks 19 shown in FIG. 5-8 are to be cold headed by machine 10, it is necessary to utilize a modified punch pin 32 in order to prevent engagement between punch 26 and the screw blank carrying structure 20. Punch pin 32' is of the same overall length as the punch pin 32, although the forward end of pin 32' is lengthened and the cylindrical collar 32a is shortened compared to pin 32. The forward end of punch pin 32 fits closely in punch aperture 30, while collar 32a fits loosely in cavity 29. Pin 32 has an enlarged flanged base 321) which is sized to closely fit in cavity 29. Outward movement of punch pin relative to punch 26 is limited by engagement of collar 32a with the shoulder formed between cavity 29 and aperture 30, a position wherein the forward end of punch pin 32 projects well beyond the forward end of punch 26.

In operation, compressor 36 is actuated by means of valve 37 and pressure regulator 38 is adjusted to deliver air at the proper pressure, which depends on the diameter of the screw that is to be operated on and which is indicated by the gauge preferably associated with regulator 38. Lubricant source 39 is also adjusted to feed the desired amount of oil hose 35. Throughout the operation of the machine, air is thereby introduced at a constant pressure into the rearward end of punch block opening 23 and behind punch 26 and punch pin 32 to continually bias the punch and pin forwardly with a constant and preselected force. Oil is also introduced into opening 23 and distributed therein under the ac tion of the compressed air to provide the required lubrication.

To cold head normal sized screws, a set length of wire stock is intially fed through the apertured inlet die (which is offset to the side of die 14) and cut by the knife to form a screw blank 19 having a preselected length. The carrying structure 20 carries screw .blank 19 sidewardly between die 14 and punch 26 and holds the blank in axial alignment with the respective apertures l5 and 30 thereof as shown in FIG. 1. The drive mechanism then operates to drive gate 13 forwardly and carry punch block 21 and punch 26 toward die, 14. One end of blank 19 enters recess-31 of punch 26. wherein it engages the forward end of punch pin 32 (which is biased forwardly by the force of the pressurized air bearing against its enlarged base 32h). Further forward movement of punch 26 under the action of the drive mechanism causes the opposite end of blank 19 to enter die aperture 15, at which time carrying structure 20 is withdrawn since the blank is supported at its opposite ends in die 14 in punch 26.

As punch 26 continues moving forwardly, the end of blank 19 engages the knockout pin 16 which is set at a depth within die aperture 15 that allows blank 19 to enter the die aperture a distance equal to the final screw length. After blank 19 engages knockout pin 16, the blank is thereafter precluded from further forward movement. When the punch is moved forwardly an additional distance the force of blank 19 overcomes the force of the air on punch pin 32, and the end of the blank partially enters aperture 30 of the forwardly moving punch. The forward end of punch 26 is eventually moved into flat engagement with die 14 immediately before base 32/) of the punch pin is backed against backing plug 25 in flat engagement therewith. At this point, which is the position shown in FIG. 2, blank 19 is completely confined within die 14 and punch 26. Once punch 26 is positioned against die 14, the punch becomes a stationary member and further forward movement of punch block 21 causes the punch to slide rearwardly within sleeve 24 and opening 23 against the force of the air pressure, although the biasing force of the air pressure continues to retain the forward face of the punch in flat engagement with die 14 as blank 19 is upset.

Punch pin 32, which is now backed against backing plug 25, is forced against the end of the confined screw blank by the forward movement of the punch block 21. Since the only space open to screw blank 19 is recess 31 of the punch, the blank is upset and caused to flow into recess 31 by the force on its opposite ends. The upsetting process continues until punch block 21 has been moved to its extreme forward position as shown in FIG. 3 and the upset metal of blank 19 has completely filled recess 31. At that time the rearward end of punch 26 becomes bottomed out against backing plug 25 and the forward end of punch pin 32 is positioned at the rearward edge of recess 31 to complete the upsetting operation and cause the partially finished screw head to take on the shape and size of recess 31. It is important to note that as screw blank 19 is being upset, the biasing force of the pressurized air on the back end of punch 26 retains the punch firmly against die 14, thereby assuring thatthe upset metal of blank 19 cannot expand beyond the recess 31.

Gate 13 is thereafter withdrawn rearwardly by the drive mechanism to carry punch block 21 and punch 26 away from die 14. The position of passage 33 at the extreme rearward end of opening 23 enables the pressurized air to be introduced directly against the forward face of backing plug 25 so that when the punch 26 and punch pin 23 are back against plug 25, the air operates to force the punch and punch pin forwardly as the latter two components are withdrawn by the rearward stroke of the drive mechanism. After completing its rearward stroke, the drive mechanism rotates the second punch 40 over into alignment with the partially finished blank. A forward stroke of the drive mechanism then rams punch 40 against the blank held in die 14 to finish the screw head in conformity with recess 43, as well as provide a screwdriver receiving recess having the shape ofprojection 44 in the screw head. The ejector mechanism (not shown) acts on knockout pin 16 in a well known manner to eject the completed screw from die 14 as a second cycle begins.

The operation of machine to cold head a very short screw 19' is best seen with reference to FIGS. 5-8. The machine operates substantially as previously described. except that a modified punch pin 32' is utilized to prevent engagement between punch 26 and carrying structure 20. As the drive mechanism drives gate 13 forwardly to move punch 26 toward die 14, punch 32 projects beyond the forward end of punch 26 due to the air pressure exerted on its enlarged base 32b. The forwardly protruding pin 32' engages blank 19 and pushes it a substantial distance into die aperture well before punch 26 approaches the carrying structure 20. Since blank 19' enters aperture 15 far enough to be supported in the proper alignment, carrying structure may be withdrawn before punch 26 has moved forwardly into engagement with same. When the forward end of blank 19' engages knockout pin 16 (which is now fixed at a lesser depth within aperture 15), the force exerted by the blank overcomes the air pressure on the punch pin and the opposite end of blank 19 enters aperture 30 of the forwardly moving punch 26.

Blank 19' is thereafter upset in the same manner as previously described. Shortly after punch 26 engages die 14, punch pin 32 becomes back against backing plug 25 as shown in FIG. 7. The force on the opposite ends of the completely confined blank 19 causes its metal to flow into punch recess 31 as punch block 21 continues to move forwardly. The sliding punch 26 is again held firmly against 14 throughout the upsetting operation by the force of the pressurized air. thus assuring that the upset metal does not expand beyond recess 31.

The second punch is thereafter rotated over and rammed into the partially finished screw head as before to finish the head and form a suitable slot or recess therein. The ejection mechanism then acts on knockout pin 16 to eject the completed screw blank from die 14.

it is noted that in cold heading very short screws, the forwardly protruding punch pin 32' must be utilized to permit the carrying structure 20 to be withdrawn at an earlier time than is normal. Otherwise, there is not enough clearance between the forwardly moving punch 26 and carrying structure 20 to prevent a collision therebctween. It is also apparent that the short blank 19' must be inserted a considerable distance into die aperture 15 before carrying structure 20 can be with drawn. It is therefore necessary to provide a means for biasing punch pin 32 to its forward position so that it pushes blank 19 well into die aperture 15 before punch 26 engages carrying structure 20. The biasing means must also be yieldable so as to permit the proper movement of punch pin 32 as the screw head is formed. It has been found that the disclosed pneumatic system is far superior as a means for biasing both punch 26 and punch pin 32', as compared to the presently existing practice of providing a separate spring for each component.

The introduction of the lubricant behind punch 26 causes the lubricant to be widely dispersed within opening 23 and forced by the pressurized air into contact with all areas of the moving parts, including punch aperture 30 and recess 31. The action of the air and lubricant not only lubricatcs the machine components in an improved manner, but also provides a cooling effect that is adequate to maintain all of the parts at a relatively low temperature even as the machine op.- erates constantly for an extended period of time, The force of the pressurized air introduced behind punch 26 blows loose particles and caked material from punch block opening 23 and punch aperture 30 to thereby prevent a buildup of dirt or other foreign material in the area behind punch 26 or in the aperture thereof.

From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, 1 claim:

1. ln an apparatus for cold heading screw blanks, said apparatus including a die having an aperture for receiv ing a portion of a screw blank, a punch having an aperture for receiving the remainder of the screw blank, means for holding the screw blank between said punch and die, means including a recess in the forward end of said punch and a pin slidably disposed in said punch aperture for forming a head on a screw blank, and power means for moving said punch toward said die to actuate 'said head forming means, the improvement comprising:

a punch block adapted for coupling to said power means in opposition to said die and having an opening for slidably receiving said punch, said opening defining a confined space rearwardly of said punch with said confined space varying in volume according to the position of said] punch in said opening, said punch block having a passage therein extending from the exterior of said punch block and terminating at the inward end of said opening to deliver air to the confined space thereof; and

an air source adapted for coupling to said passage and operable to introduce: pressurized air through said passage and into the confined space of said opening, whereby said punch is biased forwardly against said die to confine the screw blank in said punch and die apertures as said head forming means forms a head on the screw blank, while said punch is able to slide rearwardly in said opening against the biasing force of the pressurized air.

2. The improvement as in claim 1, including a pressure regulator associated with said air source and operable to maintain the air pressure substantially constant.

3. The improvement as in claim 1, including a lubricant source adapted for coupling to said passage and operable to introduce lubricant through said passage and into the confined space of said opening atthe extreme inward end thereof, whereby said pressurized air disperses said lubricant throughout said punch block opening to lubricate and cool said punch, said punch aperture and said punch recess.

4. The improvement as in claim 1, wherein said pin is adapted to extend beyond the forward end of said punch and includes an enlarged base communicating with the confined space of said punch block opening, said air source being operable to bias said pin forwardly beyond the forward end of said punch to engagingly position the screw blank in said die aperture and permit withdrawal of said screw blank holding structure before said punch engages same.

- PATENT NO.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION DATED INVENTOR(S) E 3, 906,566 September 23, 1975 Joel S. Rose It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 3, line 14,

C01. 6, line 36,

C01. 6, line 47,

C01. 8, line 29,

[SEAL] "an" should be and-.

"='" should be -32'-.

between "oil" and "hose", insert -into-.

c. MARSHALL DANN Commissioner of Patents and Trademarks RUTH C. MASON Arresting Officer 

1. In an apparatus for cold heading screw blanks, said apparatus including a die having an aperture for receiving a portion of a screw blank, a punch having an aperture for receiving the remainder of the screw blank, means for holding the screw blank between said punch and die, means including a recess in the forward end of said punch and a pin slidably disposed in said punch aperture for forming a head on a screw blank, and power means for moving said punch toward said die to actuate said head forming means, the improvement comprising: a punch block adapted for coupling to said power means in opposition to said die and having an opening for slidably receiving said punch, said opening defining a confined space rearwardly of said punch with said confined space varying in volume according to the position of said punch in said opening, said punch block having a passage therein extending from the exterior of said punch block and terminating at the inward end of said opening to deliver air to the confined space thereof; and an air source adapted for coupling to said passage and operable to introduce pressurized air through said passage and into the confined space of said opening, whereby said punch is biased forwardly against said die to confine the screw blank in said punch and die apertures as said head forming means forms a head on the screw blank, while said punch is able to slide rearwardly in said opening against the biasing force of the pressurized air.
 2. The improvement as in claim 1, including a pressure regulator associated with said air source and operable to maintain the air pressure substantially constant.
 3. The improvement as in claim 1, including a lubricant source adapteD for coupling to said passage and operable to introduce lubricant through said passage and into the confined space of said opening at the extreme inward end thereof, whereby said pressurized air disperses said lubricant throughout said punch block opening to lubricate and cool said punch, said punch aperture and said punch recess.
 4. The improvement as in claim 1, wherein said pin is adapted to extend beyond the forward end of said punch and includes an enlarged base communicating with the confined space of said punch block opening, said air source being operable to bias said pin forwardly beyond the forward end of said punch to engagingly position the screw blank in said die aperture and permit withdrawal of said screw blank holding structure before said punch engages same. 